Thin-film magnetic head structure, method of manufacturing the same, and thin-film magnetic head

ABSTRACT

A method of manufacturing a thin-film magnetic head structure comprises the steps of preparing an insulating layer  10 ; forming a first resist layer  51  provided with a first slit pattern  51   a  corresponding to a very narrow groove part and a second slit pattern  51   b  corresponding to a temporary groove part integrally extending from the very narrow groove part along outer edges of a main depression onto the insulating layer  10 ; etching the insulating layer  10  while using the first resist layer  51  as a mask; eliminating the first resist layer  51 ; forming a second resist layer having an opening pattern corresponding to the main depression onto the insulating layer  10 ; and etching the insulating layer  10  while using the second resist layer as a mask.

This application is a continuation of U.S. patent application Ser. No.11/179,728, filed Jul. 13, 2005, the entire contents of which are herebyincorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a thin-film magnetic head structure formanufacturing a thin-film magnetic head which performs perpendicularmagnetic recording operations, a method of manufacturing the same, and athin-film magnetic head.

2. Related Background Art

In recent years, the areal density in hard disk drives has beenincreasing remarkably. Recently, the areal density in hard disk driveshas reached 160 to 200 GB/platter in particular, and is about toincrease further. Accordingly, thin-film magnetic heads have beenrequired to improve their performances.

In terms of recording schemes, thin-film magnetic heads can roughly bedivided into those for longitudinal recording in which information isrecorded in a (longitudinal) direction of a recording surface of a harddisk (recording medium) and those for perpendicular recording in whichdata is recorded while the direction of recording magnetization formedin the hard disk is perpendicular to the recording surface. As comparedwith the thin-film magnetic heads for longitudinal recording, thethin-film magnetic heads for perpendicular recording have beenconsidered more hopeful, since they can realize a much higher recordingdensity while their recorded hard disks are less susceptible to thermalfluctuations.

Conventional thin-film magnetic heads for perpendicular recording aredisclosed, for example, in U.S. Pat. No. 6,504,675, U.S. Pat. No.4,656,546, U.S. Pat. No. 4,672,493, and Japanese Patent ApplicationLaid-Open No. 2004-94997.

Meanwhile, when thin-film magnetic heads for perpendicular recordingrecord data onto areas in inner and outer peripheries of a hard disk, amagnetic pole end part disposed on the side of a medium-opposing surface(also referred to as air bearing surface, ABS) opposing the recordingmedium (hard disk) yields a certain skew angle with respect to a datarecording track. In perpendicular magnetic recording heads (hereinafteralso referred to as “PMR”) having a high writing capability, the skewangle generated in the magnetic pole end part has caused a problem ofso-called side fringe in which unnecessary data are recorded betweenadjacent tracks. The side fringe adversely affects the detection ofservo signals and the S/N ratio of reproduced waveforms. Therefore, inconventional PMRs, the magnetic pole end part on the air bearing surfaceside in the main magnetic pole layer has a bevel form graduallynarrowing in width toward one direction (see, for example, JapanesePatent Application Laid-Open Nos. 2003-242067 and 2003-203311 in thisregard).

In a PMR head in which the magnetic pole end part on the air bearingsurface side of the above-mentioned main magnetic pole layer is formedlike a bevel, the width of the magnetic pole end part (hereinafterreferred to as magnetic pole width) is not sufficiently uniform, so thatit is uneven in the longitudinal direction of the main magnetic polelayer. Therefore, when the above-mentioned magnetic pole end part of themain magnetic pole layer formed on the wafer is cut at a predeterminedposition so as to define the air bearing surface of the main magneticpole layer, it has been problematic in that the magnetic pole width onthe air bearing surface may vary depending on the cutting positionTherefore, in the conventional PMR, there have been cases where thetrack width (recording track width) in the air bearing surface greatlyvaries among products.

Hence, the inventors have proposed a thin-film magnetic head structureequipped with a base insulating layer having a magnetic pole formingdepression which has been sunken into a form corresponding to the mainmagnetic pole layer beforehand and includes a very narrow groove parthaving a substantially uniform width. This magnetic pole formingdepression includes a variable width depression continuously extendingfrom an end part of the very narrow groove part while graduallyincreasing the width as distanced farther from the very narrow groovepart, and a fixed width depression continuously extending from an endpart of the variable width depression. When such a base insulating layeris used, the main magnetic pole layer is formed so as to be embedded inthe magnetic pole forming depression. Therefore, when the main magneticpole layer is cut at the very narrow groove part in the magnetic poleforming depression at the time of defining the air bearing surface, themagnetic pole width in the air bearing surface becomes the same width ata high precision.

However, the following problem may occur when forming theabove-mentioned magnetic pole forming depression into a base insulatinglayer.

The above-mentioned magnetic pole forming depression is made by thesteps of applying a photoresist onto a base insulating layer made ofalumina (Al₂O₃); patterning the photoresist using a predeterminedphotomask, so as to form a resist layer exposing the surface of the baseinsulating layer into a form corresponding to the magnetic pole formingdepression; and then performing reactive ion etching (hereinafterreferred to as RIE) while using the resist layer as a mask, so as toremove the part not formed with the resist layer. The opening width ofthe resist layer corresponding to the very narrow groove part is muchsmaller than the opening width of the resist layer corresponding to thevariable depression and fixed width depression. Therefore, whenperforming RIE using such a resist layer, radical ions substantiallyvertically enter the portion corresponding to the very narrow groove,but do not have such a directivity so much in the portion correspondingto the variable width depression and fixed width depression and arelikely to enter there in directions other than the substantiallyvertical direction as well. Consequently, in the magnetic pole formingdepression formed by RIE, the angle of inclination of side faces hasbeen smaller in the very narrow groove part than in the other parts.Therefore, the decrease in bottom area with respect to the opening areaother than the very narrow groove part is much more remarkable than thedecrease in bottom area with respect to the opening area of the verynarrow groove part, so that the volume of magnetic pole formingdepression decreases. Hence, when the main magnetic pole layer is formedby using such a magnetic pole forming depression, the quantity ofmagnetism (also referred to as magnetic volume) in the main magneticpole layer decreases, which makes it hard to further improve theoverwrite characteristic.

SUMMARY OF THE INVENTION

In order to overcome the above-mentioned problem, it is an object of thepresent invention to provide a thin-film magnetic head structure whichcan further improve the overwrite characteristic, a method ofmanufacturing the same, and a thin-film magnetic head.

For overcoming the above-mentioned problem, in one aspect, the presentinvention provides a method of manufacturing a thin-film magnetic headstructure adapted to manufacture a thin-film magnetic head comprising amain magnetic pole layer having a magnetic pole end part on a side of amedium-opposing surface opposing a recording medium; a write shieldlayer opposing the magnetic pole end part so as to form a recording gaplayer on the medium-opposing surface side; a thin-film coil wound aboutthe write shield layer or main magnetic pole layer; and a baseinsulating layer formed with a magnetic pole forming depression, filledwith the main magnetic pole layer, including a very narrow groove partdefining a form of the magnetic pole end part and a main depressionintegrally extending from an end part of the very narrow groove partremote from the medium-opposing surface; the method comprising, whenforming the base insulating layer with the magnetic pole formingdepression, the steps of forming a first resist layer on the baseinsulating layer, the first resist layer having a first slit patterncorresponding to the very narrow groove part in the magnetic poleforming depression and a second slit pattern integrally extending fromthe first slit pattern and corresponding to a temporary groove partintegrally extending from the very narrow groove part along an outeredge of the main depression; etching the base insulating layer whileusing the first resist layer as a mask; forming a second resist layerhaving an opening pattern corresponding to the main depression on thebase insulating layer after removing the first resist layer; and etchingthe base insulating layer while using the second resist layer as a mask.

When forming a magnetic pole forming depression for embedding a magneticmaterial so as to form a main magnetic pole layer, the method ofmanufacturing a thin-film magnetic head structure in accordance with thepresent invention uses two resist layers of the first and second resistlayers. Namely, the first resist layer formed with the first and secondslit patterns initially forms a very narrow groove part and a temporarygroove part integrally extending from the very narrow groove part alongan outer edge of the main depression. Subsequently, the second resistlayer forms a main depression. Therefore, when etching is performedwhile using the first resist layer as a mask, radical ions substantiallyvertically enter the portion where the base insulating layer is exposedby the first and second slit patterns, whereby the angle of inclinationbecomes quite acute at side faces of the very narrow groove part andtemporary groove part. As a result, the bottom area of the magnetic poleforming depression increases, thereby enhancing the magnetic volume inthe main magnetic pole layer, which can further improve the overwritecharacteristic.

Preferably, the etching of the base insulating layer is deeper whenusing the second resist layer as the mask than when using the firstresist layer as the mask. As a consequence, the volume of the magneticpole forming depression increases more, and embedding a magneticmaterial into the magnetic pole forming depression forms a lower yokelayer under the main magnetic pole layer, which can enhance the magneticvolume more together with the main magnetic pole layer.

Preferably, at least a part of the main depression is constituted by avariable width depression integrally extending from the end part of thevery narrow groove part remote from the medium-opposing surface andgradually increasing the width as distanced farther from the very narrowgroove part, and the second slit pattern extends along the outer edge ofthe variable width depression. In this case, when forming the mainmagnetic pole layer, the magnetic material grown in the variable widthdepression gradually enters the very narrow groove part from the endpart thereof, whereby the very narrow groove part can reliably be filledwith the magnetic material.

Preferably, the second slit pattern extends in a bifurcating fashionfrom the first slit pattern along both outer edges of the maindepression. Conventionally, the angle of inclination of side faces inthe variable width depression has been so large that the distance fromthe air bearing surface to a start point of the variable widthdepression is substantially long in the bottom face of the variablewidth depression. This has been problematic in that it causes aphenomenon known as pole erasure by which data recorded beforehand on ahard disk is erased when information is further recorded at a highdensity. The pole erasure is a phenomenon in which, after data iswritten on a recording medium (hard disk) having a high maximumcoercivity Hc, a leakage magnetic flux flows from the air bearingsurface to the hard disk even when no write current flows through athin-film coil, thereby erasing the other data. However, the presentinvention can achieve a very acute angle of inclination at side faces ofthe variable width depression, which shortens the distance from the airbearing surface to the start point of the variable width depression inthe bottom face of the variable width depression, whereby the occurrenceof pole erasure can be suppressed.

In another aspect, the present invention provides a thin-film magnetichead structure adapted to manufacture a thin-film magnetic headcomprising a main magnetic pole layer having a magnetic pole end part ona side of a medium-opposing surface opposing a recording medium; a writeshield layer opposing the magnetic pole end part so as to form arecording gap layer on the medium-opposing surface side; a thin-filmcoil wound about the write shield layer or main magnetic pole layer; anda base insulating layer formed with a magnetic pole forming depression,filled with the main magnetic pole layer, including a very narrow groovepart defining a form of the magnetic pole end part and a main depressionintegrally extending from an end part of the very narrow groove partremote from the medium-opposing surface; wherein a stepped part isformed at a boundary between a bottom face of the main depression and abottom face of the very narrow groove part.

Preferably, the bottom face of the main depression is positioned at aheight lower than that of the bottom face of the very narrow groovepart. This increases the volume of the magnetic pole forming depression,and embedding a magnetic material into the magnetic pole formingdepression forms a lower yoke layer under the main magnetic pole layer.This further increases the magnetic volume, and thus can further improvethe overwrite characteristic.

Preferably, the stepped part has an angle of inclination α fallingwithin the range of 0°<α<90°. This allows the end part of the lower yokelayer on the air bearing surface side to approach the air bearingsurface while suppressing the occurrence of pole erasure, therebyenhancing the magnetic volume accordingly, which can further improve theoverwrite characteristic.

Preferably, the distance between the stepped part and themedium-opposing surface is 0.1 to 0.3 μm. This can further improve themagnetic volume of the lower yoke layer.

Preferably, the angle of inclination in at least a part of side faces ofthe main depression is substantially the same as the angle ofinclination of a side face in the very narrow groove part. This makesthe bottom area of the magnetic pole forming depression greater thanthat conventionally obtained, and further increases the volume of themagnetic pole forming depression, with which the magnetic volume of themain magnetic pole layer can further be enhanced.

Preferably, at least a part of the main depression is constituted by avariable width depression extending integrally from the end part of thevery narrow groove part remote from the medium-opposing surface whilegradually increasing the width as distanced farther from the very narrowgroove part. In this case, when forming the main magnetic pole layer,the magnetic material grown in the variable width depression graduallyenters the very narrow groove part from the end part thereof, wherebythe very narrow groove part can reliably be filled with the magneticmaterial.

In still another aspect, the present invention provides a thin-filmmagnetic head structure adapted to manufacture a thin-film magnetic headcomprising a main magnetic pole layer having a magnetic pole end part ona side of a medium-opposing surface opposing a recording medium; a writeshield layer opposing the magnetic pole end part so as to form arecording gap layer on the medium-opposing surface side; a thin-filmcoil wound about the write shield layer or main magnetic pole layer; anda base insulating layer formed with a magnetic pole forming depression,filled with the main magnetic pole layer, including a very narrow groovepart defining a form of the magnetic pole end part and a main depressionintegrally extending from an end part of the very narrow groove partremote from the medium-opposing surface; wherein at least a part of sidefaces in the main depression has an angle of inclination substantiallythe same as that of a side face in the very narrow groove part.

In the thin-film magnetic head structure in accordance with the presentinvention, the angle of inclination in a side face of the very narrowgroove part and the angle of inclination of at least a part of sidefaces in the main depression are substantially the same. This makes thebottom area of the magnetic pole forming depression greater than thatconventionally obtained, and increases the volume of the magnetic poleforming depression. As a result, the magnetic volume of the mainmagnetic pole layer increases, whereby the overwrite characteristic canfurther be improved.

Preferably, at least a part of the main depression is constituted by avariable width depression integrally extending from the end part of thevery narrow groove part remote from the medium-opposing surface andgradually increasing the width as distanced farther from the very narrowgroove part, whereas a side face in the variable width depression has anangle of inclination substantially the same as that of a side face inthe very narrow groove part. In this case, when forming the mainmagnetic pole layer, the magnetic material grown in the variable widthdepression gradually enters the very narrow groove part from the endpart thereof, whereby the very narrow groove part can be filled with themagnetic material more reliably.

Preferably, a side face of the very narrow groove part and variablewidth depression has an angle of inclination smaller than that of a sideface of the remnant of the main depression excluding the variable widthdepression.

In still another aspect, the present invention provides a thin-filmmagnetic head comprising a main magnetic pole layer having a magneticpole end part on a side of a medium-opposing surface opposing arecording medium; a write shield layer opposing the magnetic pole endpart so as to form a recording gap layer on the medium-opposing surfaceside; a thin-film coil wound about the write shield layer or mainmagnetic pole layer; and a base insulating layer formed with a magneticpole forming depression, filled with the main magnetic pole layer,including a very narrow groove part defining a form of the magnetic poleend part and a main depression integrally extending from an end part ofthe very narrow groove part remote from the medium-opposing surface;wherein a stepped part is formed at a boundary between a bottom face ofthe main depression and a bottom face of the very narrow groove part.

The present invention will be more fully understood from the detaileddescription given here in below and the accompanying drawings which aregiven by way of illustration only, and thus are not to be considered aslimiting the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view of the thin-film magnetic head structure inaccordance with an embodiment, in which (a) is a sectional view takenalong a plane, perpendicular to an air bearing surface, intersecting athin-film coil, whereas (b) is a sectional view taken at the air bearingsurface;

FIG. 2 is a view showing an insulating layer, in which (a) is aperspective view, whereas (b) is a plan view;

FIG. 3 is a sectional view showing a major part of FIG. 2, in which (a)is a sectional view taken along the line IIIA-IIIA (sectional view takenat the air bearing surface), (b) is a sectional view taken along theline IIIB-IIIB, (c) is a sectional view taken along the line IIIC-IIIC,and (d) is a sectional view taken along the line IIID-IIID;

FIG. 4 is a view showing a main magnetic pole layer and a lower yokelayer after being cut along the air bearing surface, in which (a) is aperspective view, (b) is a plan view, and (c) is a sectional view takenalong the line C-C;

FIG. 5 is a view showing a step of the method of manufacturing athin-film magnetic head structure in accordance with the embodiment inwhich (a) is a top plan view, (b) is a sectional view taken along theline B-B of (a), and (c) is a sectional view taken along the line C-C of(a) (sectional view taken at the air bearing surface);

FIG. 6 is a perspective view showing a step subsequent to FIG. 5;

FIG. 7 is a view showing the step subsequent to FIG. 5, in which (a) isa top plan view, (b) is a sectional view taken along the line B-B of(a), and (c) is a sectional view taken along the line C-C of (a)(sectional view taken at the air bearing surface);

FIG. 8 is a view showing a step subsequent to FIGS. 6 and 7, in which(a) is a top plan view, (b) is a sectional view taken along the line B-Bof (a), and (c) is a sectional view taken along the line C-C of (a)(sectional view taken at the air bearing surface);

FIG. 9 is a perspective view showing a step subsequent to FIG. 8;

FIG. 10 is a view showing the step subsequent to FIG. 8, in which (a) isa top plan view, (b) is a sectional view taken along the line B-B of(a), (c) is a sectional view taken along the line C-C of (a) (sectionalview taken at the air bearing surface), and (d) is a sectional viewtaken along the line D-D of (a);

FIG. 11 is a view showing the step subsequent to FIGS. 9 and 10, inwhich (a) is a top plan view, (b) is a sectional view taken along theline B-B of (a), (c) is a sectional view taken along the line C-C of (a)(sectional view taken at the air bearing surface), and (d) is asectional view taken along the line D-D of (a);

FIG. 12 is a view showing a step subsequent to FIG. 11, in which (a) isa sectional view taken at a plane, perpendicular to the air bearingsurface, intersecting the thin-film coil, whereas (b) is a sectionalview taken at the air bearing surface;

FIG. 13 is a view showing a step subsequent to FIG. 12, in which (a) isa sectional view taken at a plane, perpendicular to the air bearingsurface, intersecting the thin-film coil, whereas (b) is a sectionalview taken at the air bearing surface;

FIG. 14 is a view showing a step subsequent to FIG. 13, in which (a) isa sectional view taken at a plane, perpendicular to the air bearingsurface, intersecting the thin-film coil, whereas (b) is a sectionalview taken at the air bearing surface;

FIG. 15 is a view showing a step subsequent to FIG. 14, in which (a) isa sectional view taken at a plane, perpendicular to the air bearingsurface, intersecting the thin-film coil, whereas (b) is a sectionalview taken at the air bearing surface;

FIG. 16 is a perspective view showing an insulating layer formed with aconventional cavity;

FIG. 17 is a sectional view showing a major part of FIG. 16, in which(a) is a sectional view taken along the line XVIIA-XVIIA, whereas (b) isa sectional view taken along the line XVIIB-XVIIB;

FIG. 18 is a top plan view showing a part of main magnetic pole layers,in which (a) shows the main magnetic pole layer in the embodiment,whereas (b) shows a conventional main magnetic pole layer;

FIG. 19 is a side view showing a part of main magnetic pole layers andlower yoke layers, in which (a) shows the main magnetic pole layer andlower yoke layer in the embodiment, whereas (b) shows conventional mainmagnetic pole layer and lower yoke layer; and

FIG. 20 is a view showing a step of manufacturing a thin-film magnetichead structure in accordance with a modified example, in which (a) is aperspective view, whereas (b) is a top plan view.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of the present invention will now be explainedwith reference to the drawings. In the explanation, constituentsidentical to each other or those having functions identical to eachother will be referred to with numerals identical to each other withoutrepeating their overlapping descriptions.

Configuration of Thin-Film Magnetic Head Structure

With reference to FIGS. 1 to 4, the configuration of the thin-filmmagnetic head structure 1 in accordance with an embodiment will beexplained. FIG. 1 is a sectional view of the thin-film magnetic headstructure in accordance with this embodiment, in which (a) is asectional view taken along a plane, perpendicular to an air bearingsurface, intersecting a thin-film coil, whereas (b) is a sectional viewtaken at the air bearing surface. FIG. 2 is a view showing an insulatinglayer, in which (a) is a perspective view, whereas (b) is a plan view.FIG. 3 is a sectional view showing a major part of FIG. 2, in which (a)is a sectional view taken along the line IIIA-IIIA (sectional view takenat the air bearing surface), (b) is a sectional view taken along theline IIIB-IIIB, and (c) is a sectional view taken along the lineIIIC-IIIC. FIG. 4 is a view showing a main magnetic pole layer and alower yoke layer after being cut along the air bearing surface, in which(a) is a perspective view, (b) is a plan view, and (c) is a sectionalview taken along the line C-C.

The thin-film magnetic head structure 1 in accordance with thisembodiment has a configuration adapted to manufacture a PMR head. Thethin-film magnetic head structure 1 is formed on an undepictedsubstrate, and is configured to yield a thin-film magnetic head 2 inaccordance with the present invention when cut at an air bearing surfaceS which is a medium-opposing surface opposing a recording medium (harddisk).

The thin-film magnetic head structure 1 includes a reproducing headstructure for manufacturing a reproducing head equipped with amagnetoresistive (MR) device or the like and a recording head structurefor manufacturing a recording head. FIG. 1 shows a recording headstructure formed on an insulating layer (base insulating layer) 10,while omitting the reproducing head structure.

The configuration of a major part of the recording head structure in thethin-film magnetic head structure 1 will be explained in the following,whereas the configuration of the other parts will be explained inmanufacturing steps which will be set forth later. Each constituent inthe recording head structure will be explained with the same name andnumeral before and after being cut at the air bearing surface S unlessotherwise specified. When distinguishing these states from each other,however, “′” will be added to the numeral referring to the state afterbeing cut at the air bearing surface S.

As shown in FIG. 1, the thin-film magnetic head structure 1 comprises,as the recording head structure, the insulating layer 10 and a mainmagnetic pole layer 20, a recording gap layer 26, a write shield layer30, a back magnetic pole layer 34, and a thin-film coil 40 which arelaminated on the insulating layer 10.

The insulating layer 10, which is made of alumina (Al₂O₃), is formed ata predetermined area on the above-mentioned substrate. As shown in FIG.2, the insulating layer 10 is formed with a cavity 11. The cavity 11 isa magnetic pole forming depression in the present invention, which issunken into a form corresponding to the outer shape of a main magneticpole layer 20 in order for the main magnetic pole layer 20 to attain setdimensions and shape. To this aim, the cavity 11 includes a very narrowgroove part 12, a main depression 13, and a protruded depression 16.

The very narrow groove part 12 can substantially define by its groovewidth the track width of the thin-film magnetic head 2, and thus canimprove the recording density by narrowing the track width. The length Dof the very narrow groove part 12 is set longer than a neck height NH,which will be explained later, in order to secure the air bearingsurface S at the midpoint in the length direction of the very narrowgroove part 12. The depth d₁ of the very narrow groove part 12 is set toabout 0.25 to 0.35 μm (e.g., 0.3 μm). As shown in part (a) of FIG. 3,the groove width W1 of the very narrow groove part 12 is designeduniformly in the length direction of the very narrow groove part 12, andis made much narrower than the main depression 13 in order to improvethe recording density of the thin-film magnetic head. In the very narrowgroove part 12, the groove width W2 intersecting the length direction onthe bottom face side is smaller than the groove width W1 intersectingthe length direction on the surface side such that a magnetic pole endpart 21 of the main magnetic pole layer 20, which will be explainedlater, attains a bevel form gradually narrowing in the depth direction.Namely, the angle of inclination θ₁ (which is also referred to as bevelangle) of each side face in the very narrow groove part 12 (i.e., theangle formed by the side face of the very narrow groove part 12 and aplane perpendicular to the surface of the insulating layer 10) is set toabout 7 to 12° (e.g., 10°).

Returning to FIG. 2, the main depression 13 is constituted by a variablewidth depression 14 and a fixed depression 15. The variable widthdepression 14 comprises a first variable width depression 14 a and asecond variable width depression 14 b. The first variable widthdepression 14 a extends integrally from the end part of the very narrowgroove part 12 remote from the air bearing surface S, while graduallyincreasing the groove width in a direction extending along the airbearing surface S as distanced farther from the very narrow groove part12. A stepped part 17 extending along outer edges of the first variablewidth depression 14 a is provided on the inside of the first variablewidth depression 14 a, whereas the distance from a corner part 17 aformed by the side and lower faces of the stepped part 17 to the airbearing surface S is about 0.1 to 0.3 μm, which is substantially thesame as the neck height NH (see part (d) in FIG. 3). Namely, the heightof the bottom face in the first variable width depression changes at thestepped part 17. Specifically, the height of the bottom face (defined bythe depth d₂ of the main depression 13) on the second variable widthdepression 14 b side of the stepped part 17 is lower than the height ofthe bottom face (defined by the depth d₁ of the very narrow groove part12) on the very narrow groove part 12 side of the stepped part 17 (i.e.,d₂>d₁). The second variable width depression 14 b has a groove width atthe end part on the air bearing surface S side somewhat narrower thanthat of the end part of the first variable width depression 14 a andcontinuously extends from the end part of the first variable widthdepression 14 a remote from the air bearing surface S, while graduallyincreasing the groove width as distanced farther from the first variablewidth depression 14 b. The angle of inclination θ₂ of each side face inthe first variable width depression 14 a (i.e., the angle formed by theside face of the first variable width depression 14 a and a planeperpendicular to the surface of the insulating layer 10) is set to about7 to 12° (e.g., 10°). The angles of inclination θ₁ and θ₂ are identicalto each other here, though not required to be so. The angle ofinclination α of the stepped part 17 (the angle formed by a planeforming the stepped part 17 and a plane including the bottom face of thevery narrow groove part 12 (see the broken line in part (b) of FIG. 3))is preferably greater than 0° but smaller than 90°, more preferablygreater than 0° but not more than 60°.

The fixed width depression 15 continuously extends from the end part ofthe second variable width depression 14 b remote from the air bearingsurface S while having a fixed groove width in a direction extendingalong the air bearing surface S. The angle of inclination θ₃ of eachside face in the fixed width depression 15 (the angle formed by the sideface of the fixed width depression 15 and a plane perpendicular to thesurface of the insulating layer 10) is about 12 to 20° (e.g., 18°).Namely, each of the angles of inclination θ₁ and θ₂ is smaller than theangle of inclination θ₃ of the fixed width depression 15, which is theremnant of the main depression 13 excluding the variable widthdepression 14. The protruded depression 16 continuously extends from theother end part of the very narrow groove part 12, while graduallyincreasing the groove width in a direction extending along the airbearing surface S as distanced farther from the very narrow groove part12.

The main magnetic pole layer 20′ in the present invention (as with themain magnetic pole layer 20 before cutting) is formed by filling theabove-mentioned cavity 11 with a magnetic material. Therefore, as shownin FIG. 4, the main magnetic pole layer 20′ includes a magnetic pole endpart 21′ corresponding to the very narrow groove part 12 of the cavity11 and a yoke magnetic pole part 22′ corresponding to the maindepression 13 of the cavity 11. The main magnetic pole layer 20′ has anupper face 20 a which is a flat surface without steps.

Namely, the magnetic pole end part 21′ is arranged at a position (on theair bearing surface S side) closer to the air bearing surface S than isthe yoke magnetic pole part 22′. The track width of the magnetic poleend part 21′ is uniformly defined by the very narrow groove part 12. Inthe magnetic pole end part 21′, the width W3 on the upper face 20 a sideand the width W4 on the lower face 20 b side in the direction extendingalong the air bearing surface S correspond to the groove widths W1 andW2 of the very narrow groove part 12, respectively, while each beinguniform in the extending direction of the magnetic pole end part 21′.Namely, the width W4 is narrower than the width W3 in the magnetic poleend part 21′ as in the very narrow groove part 12, thus yielding a bevelform whose width gradually decreases as distanced farther from thethin-film coil 40. The length of the magnetic pole end part 21′(distance from the air bearing surface S to the yoke magnetic pole part22′) corresponds to the neck height NH. The neck height NH is set toabout 0.1 to 0.3 μm, for example.

The yoke magnetic pole part 22′ is integrally formed from the samemagnetic material as that of the magnetic pole end part 21′, whilehaving a volume sufficiently larger than that of the magnetic pole endpart 21′. The yoke magnetic pole part 22′ includes a variable width part23 corresponding to the variable width depression 14 of the cavity 11and a fixed width part 24 corresponding to the fixed width depression 15of the cavity 11. The variable width part 23 is constituted by a firstvariable width part 23 a and a second variable width part 23 b whichcorrespond to the first variable width depression 13 a and secondvariable width depression 13 b. In the lower part of the yoke magneticpole part 22′, a lower yoke layer 25 having a form corresponding to apart of the main depression 13 is integrally formed from the samemagnetic material as that of the magnetic pole end part 21′.

Reference is now made to FIG. 1 again. The recording gap layer 26 isformed so as to be interposed between the magnetic pole end part 21 andthe insulating layer 35 and first shield part 31 of the write shieldlayer 30 which will be explained later.

The write shield layer 30 includes the first shield part 31, secondshield part 32, and third shield part 33. The first shield part 31 isformed at a position opposing the magnetic pole end part 21 by way ofthe recording gap layer 26 on the air bearing surface S side, while itslength from the air bearing surface S is about 0.1 to 0.3 μm, which issubstantially the same as the neck height NH. The second shield part 32is formed on the upper side of the first shield part 31 and backmagnetic pole layer 34, and is magnetically connected to the firstshield part 31 and back magnetic pole layer 34. The third shield part 33is formed on the upper side of the second shield part 32, and ismagnetically connected thereto.

At a position distanced farther from the air bearing surface S than isthe recording gap layer 26, the back magnetic pole layer 34 ismagnetically connected to the yoke magnetic pole part 22 and secondshield part 32. The back magnetic pole layer 34 forms a junction 36 withthe second shield part 32.

The thin-film coil 40 is positioned above the yoke magnetic pole part 22so as to bridge the variable width part 23 and fixed width part 24 byway of the back magnetic pole layer 34. While being insulated frominsulating films 37, 38, the thin-film coil 40 is wound in a planarspiral about the write shield layer 30. The thin-film coil 40 may alsobe of helical type spirally wound about the main magnetic pole layer 20or third shield part 33.

When cut at the middle part of the very narrow groove part 12 so as toform the air bearing surface S, the thin-film magnetic head structure 1having the foregoing configuration yields the thin-film magnetic head 2in the present invention.

Method of Manufacturing Thin-Film Magnetic Head Structure

A method of manufacturing the thin-film magnetic head structure 1 havingthe above-mentioned configuration will now be explained, with FIGS. 1and 5 to 15. FIGS. 5, 7 and 8 are views showing respective steps of themethod of manufacturing the thin-film magnetic head structure, in which(a) is a top plan view, (b) is a sectional view taken along the line B-Bof (a), and (c) is a sectional view taken along the line C-C of (a) (asectional view taken at the air bearing surface). FIGS. 6 and 9 areperspective views showing respective processes of the thin-film magnetichead structure. FIGS. 10 and 11 are views showing respective steps ofthe method of manufacturing the thin-film magnetic head structure, inwhich (a) is a top plan view, (b) is a sectional view taken along theline B-B of (a), (c) is a sectional view taken along the line C-C of (a)(a sectional view taken at the air bearing surface), and (d) is asectional view taken along the line D-D of (a). FIGS. 12 to 15 areperspective views showing respective steps of the method ofmanufacturing the thin-film magnetic head structure, in which (a) is asectional view taken at a plane, perpendicular to the air bearingsurface, intersecting the thin-film coil; whereas (b) is a sectionalview taken at the air bearing surface.

First, when manufacturing the thin-film magnetic head structure 1, areproducing head structure comprising an MR device and the like islaminated on an undepicted substrate made of aluminum oxide titaniumcarbide (Al₂O₃.TiC), for example. Subsequently, an insulating layer 10made of alumina (Al₂O₃) and a nonmagnetic film 41 made of Ta or the likeare formed on the upper side of the reproducing head structure (see FIG.5). The nonmagnetic layer 41 may be omitted.

Next, a photoresist is applied to the nonmagnetic film 41, and ispatterned with a predetermined photomask, so as to form a first resistlayer 51 which is opened at areas corresponding to the above-mentionedvery narrow groove part 12 and protruded depression 16, and a temporarygroove part 18 which will be explained later (see FIGS. 6 and 7).Specifically, the first resist layer 51 includes a first slit pattern 51a corresponding to the very narrow groove part 12, a second slit pattern51 b corresponding to the temporary groove part 18 extending along bothouter edges of the first variable width depression 14 a, and an openingpattern 51 c corresponding to the protruded depression 16. The secondslit pattern 51 b integrally extends from the first slit pattern 51 awhile bifurcating along both outer edges of the first variable widthdepression 14 a. Namely, the first slit pattern 51 a and the second slitpattern 51 b form a Y-shaped slit pattern. Therefore, branched slits ofthe second slit pattern 51 b extend so as to gradually increase the gaptherebetween as distanced farther from the first slit pattern 51 a. Eachof the slit width A1 of the first slit pattern 51 a and the slit widthA2 of the second slit pattern 51 b can be about 0.15 to 0.25 μm (seepart (a) of FIG. 7).

Subsequently, RIE is performed while using the first resist layer 51 asa mask, so as to eliminate the insulating layer 10 and nonmagnetic layer41 from the portion not covered with the first resist layer 51. Thisforms the very narrow groove part 12, protruded depression 16, andtemporary groove part 18. The temporary groove part 18 has a formcorresponding to the second slit pattern 51 b, and extends in abifurcating fashion from the very narrow groove part 12 while graduallyincreasing the gap between the bifurcated branches of the temporarygroove part 18 as distanced farther from the very narrow groove part 12.Namely, the very narrow groove part 12 and the temporary groove part 18form a Y-shaped groove. Here, the temporary groove part 18 defines theouter edges of the first variable width depression 14 a, so that theangle of inclination at each side face of the temporary groove part 18becomes the angle of inclination θ₂ at each side face of the firstvariable width depression. After removing the first resist layer 51, aninsulating film 42 made of alumina is formed on the whole surface of theinsulating layer 10 by ALCVD (see FIG. 8). Since the thickness of theinsulating film 42 can be controlled at a high precision, dimensions(width and depth) of the very narrow groove part 12 largely depending onthe thickness of the insulating film 42 can also be controlled at a highprecision.

Next, a photoresist is applied to the whole surface of the insulatinglayer 10 formed with the insulating film 42, and is patterned with apredetermined photomask, so as to form a second resist layer 52 providedwith an opening pattern 52 a corresponding to the above-mentioned maindepression 13 (see FIGS. 9 and 10). More specifically, the openingpattern 52 a has outer edges which are positioned on the inside of thetemporary groove part 18 and coincide with the outer edges of the secondvariable width depression 14 b and fixed width depression 15.

Subsequently, RIE is performed while using the second resist layer 52 asa mask, so as to eliminate the insulating layer 10, nonmagnetic film 41,and insulating film 42 from the portion not covered with the secondresist layer 52 (see FIG. 11). This forms the main depression 13. Here,the etching depth by RIE using the second resist layer 52 as a mask(depth d₂ of the main depression 13) is made greater than the etchingdepth by RIE using the first resist layer 51 as a mask (depth d₁ of thevery narrow groove part 12) (see FIG. 3). As a result, the stepped part17 extending along both outer edges of the first variable widthdepression 14 a is formed, and a recess corresponding to the openingpattern 52 a of the second resist layer 52 is formed. Consequently, theheight of the first variable width depression 14 a changes at thestepped part 17. Filling the recess corresponding to the opening pattern52 a of the second resist layer 52 with a magnetic material forms thelower yoke layer 25.

The foregoing steps form the cavity 11. After removing the second resistlayer 52, a nonmagnetic film 43 made of Ta or Ru is formed on the wholesurface of the insulating layer 10.

When the whole surface of the substrate is covered with the insulatingfilm 42, undepicted electrodes and the like formed on the outside of thecavity 11 are also covered with the insulating film 42. Therefore, astep of exposing the electrodes and the like is also performed by RIEusing the second resist layer 52, which makes it unnecessary to carryout a step of boring the insulating film 42 separately. As a result, thenumber of photoresists is not made greater than the conventional one,whereby the increase in cost is suppressed.

Subsequently, the cavity 11 is filled with a magnetic material (e.g.,CoNiFe) having a high saturated magnetic flux density (on the order of2.3 to 2.4 T) by plating. This forms the main magnetic pole layer 20 andlower yoke layer 25 within the cavity 11 (see FIG. 12). The surface ofthe main magnetic pole layer 20 is subjected to mechanical chemicalpolishing (which will hereinafter be referred to as CMP) as a flatteningprocess for the whole surface. Here, the nonmagnetic film 43 acts as astopper member for the CMP, so that the flattening is carried out untilit reaches the nonmagnetic film 43. Thus, the nonmagnetic film 43 formednear the very narrow groove part 12 is used for detecting the endpointof CMP, whereby the amount of polishing in the vicinity of the verynarrow groove part 12 is regulated at a high precision.

Next, the nonmagnetic film 43 exposed to the surface is eliminated byion beam etching (IBE), and then the recording gap layer 26, firstshield part 31, back magnetic pole layer 34, and insulating layer 35 areformed as shown in FIG. 13. Specifically, a coating 44 for forming therecording gap layer 24 is formed by a thickness of 400 to 500 Å so as tocover the whole surface of the substrate. For example, an insulatingmaterial such as alumina or a nonmagnetic metal material such as Ru, Ni,Cu, Ta, W, Cr, Al₂O₃, Si₂O₃, or NiPd can be used as the coating 44.Subsequently, in the coating 44, the portion to be formed with the backmagnetic pole layer 34 is opened, and the first shield part 31 and backmagnetic pole layer 34 are formed at predetermined positions. Here, thefirst shield part 31 is formed so as to oppose the magnetic pole endpart 21 by way of the recording gap layer 26 in order to define the neckheight NH. The back magnetic pole layer 34 is formed so as to join withthe yoke magnetic pole part 22 (see FIG. 4) exposed to the surface. Thefirst shield part 31 and back magnetic pole layer 34 can be formed byplating with the same magnetic material (e.g., CoNiFe or NiFe) as thatof the yoke magnetic pole part 22. Then, the insulating layer 35 made ofalumina is formed by a thickness of 1.0 to 1.5 μm, for example, so as tocover the whole surface of the insulating layer 10 and the like.

Next, the whole surface is flattened by CMP such that each of the firstshield part 31 and yoke magnetic pole layer 34 attains a thickness onthe order of 0.5 to 1.0 μm. Then, an insulating film 37 made of aluminais formed by a thickness of 0.2 to 0.3 μm so as to cover the wholesurface of the insulating layer 10 and the like. Subsequently, in theinsulating film 37, the portion to be formed with the second shield part32 is opened. On the upper side of the insulating film 37, an electrodefilm (not depicted) made of a conductive material and a frame due tophotolithography are formed, and electroplating using the electrode filmis performed, so as to form a plating layer made of Cu. As aconsequence, the plating layer and the electrode film thereunder yield athin-film coil 40, which is formed on the upper side of the yokemagnetic pole part 20 by way of the insulating film 37. Further, a frameis formed by photolithography not depicted, and the second shield part32 is formed by frame plating (see FIG. 14). The same magnetic materialas that of the first shield part 31 can be used as the second shieldpart 32. The second shield part 32 may be formed prior to the thin-filmcoil 40 as well.

Next, a photoresist 45 is applied so as to cover the whole surface ofthe insulating layer 10 and the like, an insulating layer 46 made ofalumina is formed thereon by a thickness on the order of 3.0 to 4.0 μm,and then the whole surface is flattened by CMP (see FIG. 15).Subsequently, an insulating film made of alumina is formed by athickness of about 0.2 μm so as to cover the whole surface of theinsulating layer 10 and the like, and then the insulating film is boredso as to expose the second shield part 32. This can yield an insulatingfilm 38 for insulating the thin-film coil 40 and preventing the latterfrom short-circuiting with the third shield part 33. Finally, the thirdshield part 33 is formed by a thickness on the order of 2 to 3 μm, sothat a write shield layer 30 is produced, whereby the thin-film magnetichead structure 1 shown in FIG. 1 can be obtained (see FIG. 1). When cutat the middle part of the very narrow groove part 12 so as to form theair bearing surface S, the thin-film magnetic head structure 1 formed byway of the foregoing steps yields the thin-film magnetic head 2 in thepresent invention.

Conventional Method of Manufacturing Thin-Film Magnetic Head

With reference to FIGS. 16 and 17, a conventional method ofmanufacturing a thin-film magnetic head structure will now be explained.FIG. 16 is a perspective view showing a conventional insulating layerformed with a cavity. It is a sectional view showing a major part ofFIG. 16, in which (a) is a sectional view taken along the lineXVIIA-XVIIA, whereas (b) is a sectional view taken along the lineXVIIB-XVIIB.

When manufacturing a thin-film magnetic head structure, one resist layerhas conventionally been used for forming a cavity 111 including a verynarrow groove part 112, a variable width depression 113, a fixed widthdepression 114, and a protruded depression 115. As the resist layer, aresist layer 151 provided with an opening pattern coinciding with thearea formed with the cavity 111 has been employed (see FIG. 17). Foryielding a uniform magnetic pole width, it has been necessary for theresist layer 151 to be designed such that the width A3 of the portioncorresponding to the very narrow groove part 112 is much smaller thanthe width of the portions corresponding to the variable width depression113 and the width A4 of the portions corresponding to the fixed widthdepression 114.

When RIE is performed while using the resist layer 151, the parts of theresist layer 151 positioned on both side portions of the very narrowgroove part 112 are close to each other in the portion of the resistlayer 151 corresponding to the very narrow groove part 112 as shown inpart (a) of FIG. 17. Therefore, radical ions somewhat tilted relative tothe vertical direction are blocked by the resist layer 151, so thatradical ions enter the insulating layer 10 substantially vertically. Inthe portions of the resist layer 151 corresponding to the variable widthdepression 113 and fixed width depression 114, on the other hand, theportions of the resist layer 151 positioned on both sides of thevariable depression 113 and fixed width depression 114 are greatlyseparated from each other (i.e., width A4>width A3) as shown in part (b)of FIG. 17. Therefore, radical ions arriving at the insulating layer 10while being somewhat tilted relative to the vertical direction cannot beblocked, whereby radical ions enter the insulating layer 10 fromdirections other than the substantially vertical direction as well.

Hence, in the conventional cavity 111, the angle of inclination θ₅ ateach side face of the variable width depression 113 (where the angle isformed by the side face of the variable width depression 113 and a planeperpendicular to the surface of the insulating layer 10) and at eachside face of the variable width depression 114 (where the angle isformed by the side face of the fixed width depression 114 and a planeperpendicular to the surface of the insulating layer 10) has beengreater than the angle of inclination θ₄ at each side face of the verynarrow groove part 112 (angle formed by the side face of the very narrowgroove part 112 and a plane perpendicular to the surface of theinsulating layer 10). As a consequence, the decrease in bottom arearelative to the opening area other than the very narrow groove part 112has been remarkable as compared with the decrease in bottom arearelative to the opening area of the very narrow groove part 112, thusreducing the volume of the cavity 111. This has resulted in a problemthat, when a main magnetic pole layer is formed by filling the cavity111 with a magnetic material, the magnetic volume decreases in the yokemagnetic pole part, which is a part corresponding to the variable widthdepression 113 and fixed width depression 114 of the main magnetic polelayer, thereby making it hard to further improve the overwritecharacteristic.

Further, the following problem has conventionally existed, since theangle of inclination θ₅ is greater than the angle of inclination θ₄.Namely, when a main magnetic pole layer 120 is formed by filling thecavity 111 with a magnetic material, the distance L2 a from the airbearing surface S to the start point of a yoke magnetic pole part 122 onthe upper face side of the main magnetic pole layer 120 and the distanceL2 b from the air bearing surface S to the start point of the yokemagnetic pole part 122 on the lower face side of the main magnetic polelayer 120 greatly differ from each other (see part (b) of FIG. 18). Thiscauses a problem in that the magnetic pole end part 121 is longer on thebottom face side of the main magnetic pole layer 120, whereby poleerasure is likely to occur.

By contrast, the method of manufacturing a thin-film magnetic headstructure in accordance with this embodiment uses two resist layersconstituted by the first resist layer 51 and second resist layer 52 inorder to form the cavity 11. Namely, the first resist layer includingthe first slit pattern 51 a and second slit pattern 51 b is initiallyformed on the insulating layer 10, and then RIE is performed while usingthe first resist layer as a mask, so as to form the very narrow groovepart 12 and temporary groove part 18. Subsequently, the first resistlayer 51 is removed, and RIE is performed while using the second resistlayer 52 as a mask, so as to form the main depression 13.

When performing RIE while using the first resist layer 51 as a mask, thefirst slit pattern 51 a and second slit pattern 51 b in the insulatinglayer 10 expose only the portion corresponding to the very narrow groovepart 12 and temporary groove part 18, so that radical ions enter theinsulating layer 10 substantially vertically in thus exposed portion.Consequently, not only the angle of inclination θ₁ of the very narrowgroove part 12 but also the angle of inclination θ₂ of the side faces inthe first variable width depression 14 a becomes very acute. As aresult, the bottom area of the cavity 11 becomes greater than thatconventionally attained, thereby increasing the volume of the verynarrow groove part 12. Therefore, when the main magnetic pole layer 20is formed by using the cavity 11, the magnetic volume of the mainmagnetic pole layer 20 can further be enhanced, whereby the overwritecharacteristic can further be improved.

In addition, the angle of inclination θ₂ of the side faces in the firstvariable width depression 14 a becomes very acute, so that, when themain magnetic pole layer 20 is formed by filling the cavity 11 with amagnetic material as shown in part (a) of FIG. 18, the differencebetween the distance L1 a from the air bearing surface S to the startpoint of the yoke magnetic pole part 22 on the upper face side of themain magnetic pole layer 20 and the distance L1 b from the air bearingsurface S to the start point of the yoke magnetic pole part 22 on thelower face side of the main magnetic pole layer 20 is much smaller thanthat attained conventionally. As a result, the magnetic pole end part 21becomes very short on the bottom face of the main magnetic pole layer20, thereby making it possible to suppress the occurrence of poleerasure.

The etching depth d₂ of the insulating layer 10 when using the secondresist layer 52 as a mask is greater than the etching depth d₁ of theinsulating layer 10 when using the first resist layer 51 as a mask inthe method of manufacturing the thin-film magnetic head structure 1 inaccordance with this embodiment, so that the stepped part 17 is formedat the boundary between the bottom face of the main depression 13 andbottom face of the very narrow groove part 12 in the cavity 11.Consequently, embedding a magnetic material into the cavity 11 forms thelower yoke layer 25 in addition to the main magnetic pole layer 20.Therefore, the magnetic volume can further be increased.

Since the lower yoke layer 225 has conventionally been formed byplating, the angle γ formed by the end face of the lower yoke layer 225on the air bearing surface S side and the lower face of the mainmagnetic pole layer 120 (see the broken line in part (b) of FIG. 19) hasbeen 90°. Therefore, when the end face of the lower yoke layer 225 onthe air bearing surface S side is positioned closer to the air bearingsurface S, magnetic fluxes leak from the lower yoke layer 225 to therecording medium, thereby generating the pole erasure. Hence, it hasbeen necessary for the lower yoke layer 225 to be formed with a distanceof about 1 μm from the air bearing surface S in order to prevent thepole erasure from occurring.

In this embodiment, however, the stepped part 17 is formed within thecavity 11 and has an angle of inclination α as shown in part (b) of FIG.3. The cavity 11 is filled with a magnetic material, whereby the loweryoke layer 25 is formed such that the angle β formed by the end face ofthe lower yoke layer 25 on the air bearing surface S side and the lowerface of the main magnetic pole layer 20 (see part (a) of FIG. 19) is thesame as the angle of inclination α of the stepped part 17. Consequently,the angle δ formed by the lower face of the lower yoke layer 25 and theend face 25 a of the yoke layer 25 on the air bearing surface S becomesan obtuse angle greater than 90°, thereby suppressing the leakage ofmagnetic fluxes from the part with the angle δ. As a result, theoccurrence of pole erasure can be suppressed while placing the loweryoke layer 25 closer to the air bearing surface S than in conventionalcases, whereas the magnetic volume increases as the lower yoke layer 25approaches the air bearing surface S, so that the overwritecharacteristic can further be improved.

Though a preferred embodiment of the present invention is explained indetail in the foregoing, the present invention can be modified invarious manners without being restricted to the above-mentionedembodiment. When employing a cavity 11 in which a fixed width depression15 continuously extends from the end part of the first variable widthdepression 14 a remote from the air bearing surface S, for example, asecond resist layer 53 provided with an opening pattern 53 acorresponding to the first variable width depression 14 a and fixedwidth depression 15 and including shoulders 53 b may be used as shown inFIG. 20 after using the above-mentioned first resist layer 51 as a mask.In this case, the angle of inclination θ₁ of side faces in the verynarrow groove part 12 and the angle of inclination θ₂ of the side facesin the first variable width depression 14 a are formed very acute by thefirst resist layer 51, so that the magnetic volume of the yoke magneticpole part 22 can be increased. Also, the second resist layer 53 includesthe shoulders 53 b, by which the magnetic volume of the yoke magneticpole part 22 can be made greater than that in the above-mentionedembodiment.

Though this embodiment shows a mode in which the second slit pattern 51b corresponds to both outer edges of the first variable width depression14 a, the second slit pattern 51 b may correspond to the whole outerperiphery of the variable width depression 14 or main depression 13.

1. A thin-film magnetic head structure adapted to manufacture athin-film magnetic head comprising a main magnetic pole layer having amagnetic pole end part on a side of a medium-opposing surface opposing arecording medium; a write shield layer opposing the magnetic pole endpart so as to form a recording gap layer on the medium-opposing surfaceside; a thin-film coil wound about the write shield layer or the mainmagnetic pole layer; and a base insulating layer formed with a magneticpole forming depression, with the main magnetic pole layer as the onlymagnetically functional layer in the depression, including a very narrowgroove part defining a form of the magnetic pole end part and a maindepression integrally extending from an end part of the very narrowgroove part remote from the medium-opposing surface; wherein a steppedpart is formed at a boundary between a bottom face of the maindepression and a bottom face of the very narrow groove part.
 2. Athin-film magnetic head structure according to claim 1, wherein thebottom face of the main depression is positioned at a height lower thanthat of the bottom face of the very narrow groove part.
 3. A thin-filmmagnetic head structure according to claim 2, wherein the stepped parthas an angle of inclination α falling within the range of 0°<α<90°.
 4. Athin-film magnetic head structure according to claim 1, wherein theangle of inclination in at least a part of side faces of the maindepression is substantially the same as the angle of inclination of aside face in the very narrow groove part.
 5. A thin-film magnetic headstructure according to claim 1, wherein at least a part of the maindepression is constituted by a variable width depression extendingintegrally from the end part of the very narrow groove part remote fromthe medium-opposing surface while gradually increasing the width asdistanced farther from the very narrow groove part.
 6. A thin-filmmagnetic head structure adapted to manufacture a thin-film magnetic headcomprising a main magnetic pole layer having a magnetic pole end part ona side of a medium-opposing surface opposing a recording medium; a writeshield layer opposing the magnetic pole end part so as to form arecording gap layer on the medium-opposing surface side; a thin-filmcoil wound about the write shield layer or the main magnetic pole layer;and a base insulating layer formed with a magnetic pole formingdepression, with the main magnetic pole layer as the only magneticallyfunctional layer in the depression, including a very narrow groove partdefining a form of the magnetic pole end part and a main depressionintegrally extending from an end part of the very narrow groove partremote from the medium-opposing surface; wherein at least a part of sidefaces in the main depression has an angle of inclination substantiallythe same as that of a side face in the very narrow groove part.
 7. Athin-film magnetic head structure according to claim 6, wherein at leasta part of the main depression is constituted by a variable widthdepression integrally extending from the end part of the very narrowgroove part remote from the medium-opposing surface and graduallyincreasing the width as distanced farther from the very narrow groovepart; and wherein a side face in the variable width depression has anangle of inclination substantially the same as that of a side face inthe very narrow groove part.
 8. A thin-film magnetic head comprising amain magnetic pole layer having a magnetic pole end part on a side of amedium-opposing surface opposing a recording medium; a write shieldlayer opposing the magnetic pole end part so as to form a recording gaplayer on the medium-opposing surface side; a thin-film coil wound aboutthe write shield layer or the main magnetic pole layer; and a baseinsulating layer formed with a magnetic pole forming depression, withthe main magnetic pole layer as the only magnetically functional layerin the depression, including a very narrow groove part defining a formof the magnetic pole end part and a main depression integrally extendingfrom an end part of the very narrow groove part remote from themedium-opposing surface; wherein a stepped part is formed at a boundarybetween a bottom face of the main depression and a bottom face of thevery narrow groove part.